Adenosine deaminase gene therapy(Genetic Therapy, Inc.)

ATP consumption during intense neuronal activity leads to peaks of both extracellular adenosine levels and increased glucose uptake in the brain. Here, we investigated the hypothesis that the activation of the low-affinity adenosine receptor, the A2B receptor (A(2B)R), promotes glucose uptake in neurons and astrocytes, thereby linking brain activity with energy metabolism. To this end, we mapped the spatiotemporal accumulation of the fluorescent-labelled deoxyglucose, 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG), in superfused acute hippocampal slices of C57Bl/6j mice. Bath application of the A(2B)R agonist BAY606583 (300 nM) triggered an immediate and stable (>10 min) increase of the velocity of 2-NBDG accumulation throughout hippocampal slices. This was abolished with the pretreatment with the selective A(2B)R antagonist, MRS1754 (200 nM), and was also absent in A(2B)R null-mutant mice. In mouse primary astrocytic or neuronal cultures, BAY606583 similarly increased (3)H-deoxyglucose uptake in the following 20 min incubation period, which was again abolished by a pretreatment with MRS1754. Finally, incubation of hippocampal, frontocortical, or striatal slices of C57Bl/6j mice at 37 °C, with either MRS1754 (200 nM) or adenosine deaminase (3 U/mL) significantly reduced glucose uptake. Furthermore, A(2B)R blockade diminished newly synthesized glycogen content and at least in the striatum, increased lactate release. In conclusion, we report here that A(2B)R activation is associated with an instant and tonic increase of glucose transport into neurons and astrocytes in the mouse brain. These prompt further investigations to evaluate the clinical potential of this novel glucoregulator mechanism.

A study was made to determine if constitutively active adenosine receptors are present at mouse motor nerve endings. In preparations blocked by low Ca(2+)/high Mg(2+) solution, 8-cyclopentyl-1,3,dipropylxanthine (CPX, 10-100 nM), which has been reported to be both an A(1) adenosine receptor antagonist and inverse agonist, produced a dose-dependent increase in the number of acetylcholine quanta released by a nerve impulse. Adenosine deaminase, which degrades ambient adenosine into its inactive congener, inosine, failed to alter the response to 100 nM CPX. 8-Cyclopentyltheophylline (CPT, 3 μM), a competitive inhibitor at A(1) adenosine receptors, prevented the increase in acetylcholine release produced by CPX. At normal levels of acetylcholine release, neither adenosine deaminase nor CPX affected acetylcholine release at low frequencies of nerve stimulation in (+)-tubocurarine blocked preparations. The results suggest that a proportion of the acetylcholine release process is controlled by constitutively active adenosine receptors at murine motor nerve endings, providing the first evidence for constitutive activity of G-protein-coupled receptors that modulate the function of mammalian nerve endings.